DynaFlite Bird of Time ARF Statement

[Bax]

Dynaflite Bird Of Time ARF Wing Structure Statement


Dynaflite is aware of a small percentage of reported Bird Of Time ARF wing failures. We will react to these reports as best we can to service loyal Dynaflite customers.

Dynaflite and Dynaflite's factory are examining this situation and will make changes to further strengthen the Bird Of Time ARF wing structure. The percentage of wing failures is very small in relation to the number of Dynaflite Bird Of Time ARFS that have been sold to date ( less than 1.5%). The vast majority of Bird Of Time ARF owners and flyers have had no wing failures that Dynaflite is aware of, and are very happy with the ease of assembly and overall flight performance.

Dynaflite has a rigorous stress testing procedure for new airplane kits and ARF models. None of Dynaflites stress testing revealed a weakness in the prototypes of the Bird Of Time ARF wings during winch and hi start launching. Winch launching was conducted in a reasonable and realistic manner, knowing the wings could be folded with an overzealous use of the winch.

Please keep in mind when winch launching any sailplane, including all composite structure type sailplanes, the airframe and wings can be overstressed and destroyed, if sensible use of the winch is not utilized. Use of the winch can only be controlled and monitored by the user. A sailplane with a thin airfoil using a balsa/ply built-up wing structure will not take the same type of winch launch that a composite-construction sailplane wing will. It is the non-discretionary use of the winch that generally leads to sailplane wing failures.

-FULL PEDAL LAUNCHES WITH THE BIRD OF TIME ARF SHOULD NOT BE ATTEMPTED!!!
-THE PROBABILITY OF A WING FAILURE WITH A WINCH IS MUCH HIGHER THAN WITH A HI START!!!
-IF YOU MUST USE A WINCH TO LAUNCH YOUR BIRD OF TIME ARF, PLEASE BE VERY CAREFUL, AND USE THE WINCH PEDAL RESPONSIBLY!!!

If you have any difficulty with your Bird Of Time ARF wings, please feel free to contact us, and we will do our best to remedy your situation.

If your Bird Of Time ARF wing has failed, please contact us so we can send you a prepaid shipping label to bring the entire plane back to us. Once we have your Bird Of Time ARF back and available to examine and evaluate, we can give you options regarding a replacement or exchange for another plane,.

Dynaflite apologizes for any inconvenience linked to reports, and/or actual failures, of the Bird Of Time ARF wings during launching.

Support: (217) 398-8970
Web: http://www.dynaflite.com/index.html

[Ollie]

BAX,

Would you please, be more specific in describing your "rigorous stress testing proceedure?" If these stress tests were quantitative, what were your measurement results?

What size fusible link would you recommend to insure that a gust, a strong histart in a good wind or inexpert operation of the winch would not fold ARF BOT wings?

[MTT]

Ollie, I would be very surprised if you get an answer to that, I mean a real, comprehensive answer, not spin doctoring......

Judging from the way Dynaflite has handled this so far, the statement that they did rigorous stress testing sounds like BS to me.


And :
-FULL PEDAL LAUNCHES WITH THE BIRD OF TIME ARF SHOULD NOT BE ATTEMPTED!!!
-THE PROBABILITY OF A WING FAILURE WITH A WINCH IS MUCH HIGHER THAN WITH A HI START!!!
-IF YOU MUST USE A WINCH TO LAUNCH YOUR BIRD OF TIME ARF, PLEASE BE VERY CAREFUL, AND USE THE WINCH PEDAL RESPONSIBLY!!!

Why didn't they say so from the beginning ?
They can't tell me they didn't expect folks to put this thing on the winch.

Michael

[Ollie]

MTT,

I am trying to give Dynaflite the benefit of any doubt and I stand ready to change my mind and even recommend their product if they convince me that this is not a design problem and is a relatively rare quality control slipup.

The history of the Spirit kit wing joiner is that the original joiner was all plywood and the kit was later strengthened by adding an aluminum insert. In my judgement, that was a design problem that they corrected. History seems to be repeating itself.

[MTT]

I am trying to give Dynaflite the benefit of any doubt

So do I !
But like you say yourself, past history is not encouraging......

If they really did rigorous stress testing ( I love that phrase ! ;) ) neither the Spirit wing joiner thing nor this would have ever happened.

Michael

[Ollie]

MTT,

And,"Those who do not learn from history are doomed to repeat it."

[schrederman]

I went to the site and looked at the addendum, and I fear a gloss over. This is especially troublesome when they claim 1.5 % failure rate. I have had manufacturers claim that "I am the only one having these troubles out of the millions of these sold," when in fact, talking to others with the same product, we all got together and sued...successfully, I might add. What a shame for those expecting a fix. If I were Dave Thornberg, I'd be very disappointed in what they did with my design. We have thus far had a 90% fail rate of the ones I've seen around Houston...

Back at ya, Bax....

Jack Womack

[Superman]

I and one other club member in my club have these. I am wondering what they define "failure" as because both of ours dont hold up on the winch well. Mine flexes A LOT and I tap the whole way up and have a very delicate launch. I took off the covering on the center section to reenforce it and the joiner boxes were broken and also had to be renforced. The wing didnt snap while flying. I would consider this a failure even thought the wing did not fold in flight... All in all, I think after I reenforce this and add spoilers, I will love this airplane but I dont think it is that great of a plane when flown stock...

-Clark

[Miami Mike]

Can't you guys read? There's no problem with the wings, and they're working right now to fix the problem.

I feel better already.

[Ollie]

Thanks Mike!

Laughter is the best medecine and now I feel better too.

[R. Carver]

Originally posted by Miami Mike
Can't you guys read? There's no problem with the wings, and they're working right now to fix the problem.

I feel better already.

LOL.... Riiiight :D

[ohbut6is9]

I was wondering where the Iraq information minister was working Thanks Dyna Flight:confused: I really enjoy buying products from companys that use the Jedi mind trick on their customers...

[sierra-gold]

I realize that this post is slightly off the BOT subject, but it concerns ARF quality.

There is a large base of "quality building" techniques developed by modelers over many years of building and "test" flying. Some of these techniques do not lend themselves to volume production.

I think the BOT horizontal grain shear webs is one. Much easier to grind out shear webs that way. As a newbie in 1975, I built my Square Soar that way.

I recently purchased a Hanger 9 Aspire glider. While admiring the overall quality of the glider (considering the price) I accidently gripped the fuse to firmly and cracked the fuse top sheeting. Close examination revealed that the top and bottom fuse sheeting had been cut as one piece with the grain running length wise. Now, I am just returning to the hobby after an 11 year hiatus, but one of the things I learned in the 70s and 80s in building kits was that fuse sheeting should be applied with the grain running across the fuse for strength. But this results in 6-12 pieces to be cut and sanded off... not good for production costs!

I don't want to even think how my Aspire wing is built, but fortunately I'm looking to fly it with EP for launching and liesurely sport flying. (A close look through the transparent covering reveals vertical grain shear webs, anyhow.) For $80, it appears to be a good deal for my intended use. Oh yeah, I did replace the fuse top and bottom sheeting.

We modelers who enjoy flying more than building, or who don't have time to build, will have to "vote with our consumer dollars" and put out the word on forums like this, to educate and warn consumers. We may even educate a few companies along the way. :D

Bob Goldsmith
AMA 12351

[dgliderguy]

Bob Goldsmith,

My take exactly! The longitudinal grain direction on the shear webs and the fuselage top/bottom sheeting is a short cut that crept in on the production line. I see beginners do this all the time, thinking all they have to do is get the thing sheeted, and the easiest way is to cut the pieces the long direction. This is the price of offloading to low-income, low-skill workers and looking the other way on production techniques. I thought the $149 street price on the BOT ARF was a real bargain considering all you get for your money, but now I guess I can see how it is done. Still, there is a lot of quality work on the BOT ARF kit, like the really nice looking fuselage and the overall fit and trim.

BTW, mine is holding up just fine. Lots of launches on my shortie hi-start and no sign of wing weakness.... yet!

Don Bailey

[sierra-gold]

My intention of this post is not to defend ARF manufacters, but to post an additional observation.

I went to my first glider contest in about 12 years (as a spectator) a couple of months ago... the Spring Fling in Davis. I couldn't believe the launches! :eek:

I got to see an AVA there. Now that is some kind of ARF! In RES class it launched like the "big guys." I'm not sure of the cost, but I'll say $500 for conversation. It may be more.

Perhaps we expect too much of ARF planes that cost $50 to $150. I know this, if I were planning to seriously campaign a RES class glider on a local club level, I wouldn't do it with a $150 ARF glider using todays winches. That is asking too much IMHO. I think one has to buy a kit and "beef" it up for that kind of stress. Or, spend $400 and up, for a well built glider that will withstand the stress.

Maybe there is a place for both types of ARFs? ;) As long as we understand the limitations of the less expensive ARFs.

I know I wouldn't buy a BOT kit for $80, build it, and then offer to sell it to someone for $150 as a business venture. Would you? Hell, two rolls of Monokote cost $25.

My point... if flown carefully and gently off a high start or pulsing on a winch, apparently the BOT ARF works and looks beautiful soaring across the sky.

Maybe I even can support the ARF BOT with my dollars considering my intended use of an electric motor in the front and a trip down memory lane with that classic look floating across the field.

Just my thoughts,

Sierra Gold
AMA 12351

[MTT]

sierragold and gliderguy, I think you both have a point in your observations, it is obvious that you can't expect to get top quality and materials for the price at which the BOT ARF is offered.

The mistake of Dynaflite ( GP, Hobbico, whoever... ) however, is not to present the facts straight right from the beginning.
Only after numerous posts about the BoT's wing strength ( or lack of it ) they respond to the issue, and come out with this :

-FULL PEDAL LAUNCHES WITH THE BIRD OF TIME ARF SHOULD NOT BE ATTEMPTED!!!
-THE PROBABILITY OF A WING FAILURE WITH A WINCH IS MUCH HIGHER THAN WITH A HI START!!!
-IF YOU MUST USE A WINCH TO LAUNCH YOUR BIRD OF TIME ARF, PLEASE BE VERY CAREFUL, AND USE THE WINCH PEDAL RESPONSIBLY!!!

I said it before, they must have been aware that folks would put this thing on the winch. There are still lots of people out there using hi-starts, but the trend is towards winches, with the Ford longshaft motor on 12V being the standard.

Michael

P.S. I think the AVA is closer to $ 700.-

[schrederman]

I've posted this in a couple of places so if you've seen it already, sorry..... A fix for this model cam be had by removing the Monokote from the wing, and ripping the spar section out on a radial arm saw or table saw. Sounds gastly, but it works. Now build a spar as you want, and epoxy the leading and trailing sections to the new spar. It will be heplfil to leave about 1/16" of the spar on the trailing section to help steady the ribs in this operation, and keep them aligned for the glue up process. This is possible, and not a thoery by some insane scratch builder. I did this for a friend last year on a poorly done Sailaire that he had bought. We used a 7/16" steel joiner in a new spar and he doesn't get any of the tip-touch launch syndrome...heck, he doesn't flex the wing at all. He can even zoom it! This could be done in an easy weekend, especially if the spar was built ahead of time.

I know most of you won't try this, as you bought something that should be an ARF. But if you have to have one of these and want more wing strength, this is one way to get it.

Add spoilers while you're in there and viola!!

Enjoy

Jack Womack

[Hawksnest]

Originally posted by sierra-gold
My intention of this post is not to defend ARF manufacters, but to post an additional observation.


I got to see an AVA there. Now that is some kind of ARF! In RES class it launched like the "big guys." I'm not sure of the cost, but I'll say $500 for conversation. It may be more.

I know this, if I were planning to seriously campaign a RES class glider on a local club level, I wouldn't do it with a $150 ARF glider using todays winches. you? Hell, two rolls of Monokote cost $25.

AMA 12351
I just have to step in here. At the nats, at least two AVAs blew the tips off on the winch, that's $700 worth of ARF each. Three weeks ago at a contest, I watched a friend of mine launch the maiden flight of his new $700 AVA, yup, it blew the tips off on a very mild launch and mild zoom. He will be waiting for at least 40 to 60 days for replacement parts from Europe. The poly joint where it broke (both sides) had a tiny metal joiner 1/2" extended into each side, and tore out the carbon spar and balsa ribs, both sides of the breaks. This was typical of many I/we have now heard of. It looked like a total crap joint build IMHO. So please don't think that throwing big dollars at something makes it any better if sound building practices aren't being used. Yes, my friend and I are upset over this, and now he is without a plane, as are others, as they decide if there is a "problem". Be very happy you have a $150 plane. Actually my BOT was $135 with a coupon, and three hours to rebuild the spar. Off the soapbox now. Bill G.

[blumj]

The issues with the ARF BOT are not unique. This same "armchair engineering analysis" could be leveled against any airframe that has experienced failure. To name a few:

I folded the wing on my hotliner, only to find that it is obechi over foam with no spar. Everyone knows that a wing with a spar structure is stronger(also heavier and more expensive to manufacture) than one without. The fact that I pulled out abruptly from a 100 mph dive needs to be considered in this analysis.

My expensive F3b glider experiences wing flutter and crashes. Analysis shows that the molded wing did not use cloth laid at a 45 degree bias. Everyone knows that a wing built on a 45 degree bias is torsionally stiffer(also more expensive) than one with cloth at 90 degrees. I want my money back!

My expensive scale discus glider experiences aileron flutter during
fast passes. I think in the future Mr Krause should provide wing flow analysis on his products. I want my money back!

I could go on and on - these are true stories.

It sounds like the ARF BOT wing spar is not well engineered/well built. What did you want for $149?

Oh btw, I bought a $4 bottle of wine from Chile last night. Tasted like sh*&^^&! Everyone knows that if you use good grapes and age wine for years you get a better product. I want my money back!

[Miami Mike]

Originally posted by blumj
It sounds like the ARF BOT wing spar is not well engineered/well built. What did you want for $149?I wanted a plane that would hold together and fly. I wouldn't pay $1.49 for what I got.

[Ollie]

So, if every one of the nay sayers is to be believed:

Industry standards for wing strength are not practical or achievable.
Product reviewers can't or won't protect customers from shoddy products.
Customers can't differentiate good from bad products by price.
Any one who buys an ARF is taking a big risk.
Appearance is more important than structure for the purchase decision.
First time consumers are the easiest to victimize.
It's the customers fault for using winches imprudently.
It's not really a problem because it happens so infrequently.
ARFs are the only way a growing number of people can or will participate.
You can trust and be loyal to the supplier because they do rigorous testing.
It hasn't happened to me yet so there isn't a problem.

I hope I haven't left anyone's opinion out of this summary.

This must be generally acceptable in the market since the sales of ARFs are growing rather than declining. There are or have been waiting lists to buy the two most resent examples of products with failing wings.

You are wasting your time complaining because your fate is sealed. Don't worry, be happy.

My personal opinions are:

You won't know what is under the covering unless you cover it yourself.
You won't know what it is built with unless you build it yourself.
You won't know what it is designed to do unless you design it yourself.
(Maybe not even then, depending on your knowledge and skill.)

This is not a hobby/sport for the risk averse.

[jrgospod]

Blumj

How would you have felt if the analysis of your broken hotliner had revealed obvious design/build errors/problems like the BOT horizontal grain shear webs? What if the grain on the obechi was running the wrong way? I think you would have been singing a different song. I feel that all planes have limits, but if the assembly is wrong and concealed so you could not know, then you have a gripe and the manufacture has a responsibility.

John

[schrederman]

Well,

This has sparked a real interest in building here in Houston. We decided to do a club RES project and teach people to build. It's nice to be admired, but people standing around the back of my pickup saying, "Gee, I wish I could build like that," gets old. We decided to share our knowledge with all that would participate. I was astonished to see 18 of our 33 members signed up to build one of these. We begin tomorrow with a layup class for the fiberglass fuselage. The plans are done in CAD and are being polished up for plotting, and the instructions and material lists are published. The rib and web files have gone to Dave Meyers of Laserarts along with a check for multiple sets. I have had to ask people not to try to order these yet to give us a chance to get them checked, as Dave has already heard form several members.

Why am I ragging about this here? If you don't like to see friends ripped off by the ARF market ... maybe you should do something about it ... something POSITIVE ...

Stepping politely off the soapbox and returning to my usual bland demeanor...

Jack Womack
President (reluctantly)
Houston Hawks

BTW: The project is called the "HOUSTON HAWK" ... what else?

[Ollie]

Jqck,

I hope you will start a thread and share your project with us as it progresses. I wish I could be in Houston to participate.

Give my regards to Don Cleveland if he is around.

Best Regards,
Ollie

[schrederman]

Don's house is where we're going to layup a fuselage tomorrow. One of our members is going to do an article for publication in RCSD I believe. I'll do some pics and a thread here, too.

Jack

[kingbee]

Jack,
To be such a talented builder and able to teach as well is a gift. I know from my professional life that I make a lousy teacher. My hat is off to you.

Here's hoping that all 18 complete the project. Should be able to hold a great one-design contest!

Cheers,
Dave

[blumj]

My original post may have seemed insensitive to those who have experienced failures with their ARF BOT. I to, have lost ARF's due to design and manufacturing methods that were not consistent with the intended purpose of the aircraft.

I must say for the most part the failing aircraft were priced too low to be true. As it turns out they were!

Years ago I had seen an Aeronaut Sunfly hotliner fly at the KRC electric meet on 27 cells with an Astro 60 motor. The pilot put it through many high stress maneuvers. The strength of the design was impressive.

Hobby Lobby sold the Sunfly from many years at $400. More than I had to spend at that time. A few years ago it appeared in the Hobby Lobby catalog for $225. It was still being touted as a strong hotliner, capable of 100 mph dives. I bought it immediately. On the first high speed dive the wing fluttered. At moderate speeds the sunfly flew just beautifully. Eventually I folded the wing. Inspection revealed balsa over white foam with a layer of 3 oz. fiberglass - NO SPAR.

It just so happened I owned another Freudenthaler design at the time - a Surprise 2. This was $400 new from Ed SLegers. When this plane finally met it's demise after years of flying and untold high speed runs with less than perfect pullouts, I cut into the wing to examine it's construction. Balsa over white foam with carbon I beam spar, solid vertical ply shearweb, and carbon cloth top and bottom to 3/4 span. I am sure thisi s how the $400 Sunfly was originally built.

So the $225 Sunfly was too good to be true and it sounds like the $149 BOT is too.

Other apparently "well built/well designed" 3 meter winchable ARF sailplanes seem to sell for $400 - $800.

Like my $4 bottle of Chilean wine which showed a nice vineyard on the label and touted "robust, full flavor with hints of raspberry", these too good to be true ARF are just that.

Basically you get what you pay for. I have learned this lesson the hard way.

[sierra-gold]

Originally posted by schrederman
Well,
This has sparked a real interest in building here in Houston. We decided to do a club RES project and teach people to build. It's nice to be admired, but people standing around the back of my pickup saying, "Gee, I wish I could build like that," gets old. We decided to share our knowledge with all that would participate.

Wonderful idea! I started flying RC gliders when I was 36 and joined a local club. They used to have a "show and tell" at some meetings, but it was more of a "look at my newest toy" than an instructional resource. As a new member I suggested that some of the experienced guys do some real basic construction to demo the correct methods. It got vetoed.

I taught myself to build and built 10-15 kits over the next 15 years. But still don't consider myself a "good builder" today ... 25 years later.

More clubs should consider basic "how to" demos to take the mystery out of building and to teach good building techniques to newer members. I'm sure I would be surprised at what I don't know... or maybe I wouldn't be surprised!
:D :D

Sierra Gold

[jrgospod]

blumj,


Just so no one gets the wrong impression of "cheep" Chilean wines; the quality of wine is not in always in the price. Two years ago this fall my wife and I spent 3 weeks in Chile and the “cheap” wine was great. We would stop at vineyards and pick the ones we enjoyed. I remember in particular that the night before we left we bought the most expensive they had, a very nice red to have for supper. When I went to pay it was less then $2.00 a bottle for a great vintage.

John

[Jim M2]

Originally posted by blumj
It just so happened I owned another Freudenthaler design at the time - a Surprise 2. This was $400 new from Ed SLegers. When this plane finally met it's demise after years of flying and untold high speed runs with less than perfect pullouts, I cut into the wing to examine it's construction. Balsa over white foam with carbon I beam spar, solid vertical ply shearweb, and carbon cloth top and bottom to 3/4 span. I am sure thisi s how the $400 Sunfly was originally built.

[/B]

No it wasn't. There were two Sunfly's: one was made in the style of his contest airplane and was either made by Freudenthaler or under his supervision, and the other was the AeroNaut version which had a foam wing with glass cloth and no spars. The AeroNaut version is the only version Hobby Lobby ever carried, and the wing construction was always foam, glass cloth and wood sheeting. There was no difference in construction between any of the Sunflys that Hobby Lobby sold.

Jim Martin

[Miami Mike]

Originally posted by jrgospod
Just so no one gets the wrong impression of "cheep" Chilean wines; the quality of wine is not in always in the price...This is just a short reminder, folks. This thread concerns people who bought an ARF Bird of Time glider made by Dynaflite. There was a defect discovered and we're concerned about what the factory will be doing about it. It would really be nice if you folks who didn't even buy one of these planes, and prefer to discuss the general virtues of ARF vs. kit planes, or how much value one ought to expect for one's money, would please stop disrupting this thread and start one of your own instead.

Thank you.

[ohbut6is9]

Right On Mike!!!!!!!!!!!!!

[rdawson]

Hello,
I built the Bird of Time and have made a power pod for it. See pics. It has a OS Max 10 on it with a Hayes 2oz fuel tank and a servo for throttle control. The whole unit weighs
13oz. The glider weighs in at 63 oz plus 13 oz for the pod for a total of 76oz. The weight make the wing loading 10.30 oz per sq ft. The pod is held on with rubber bands. Next week you can go to my youtube page and see the build and flight review including building the power pod. Search rdawson55 at you tube aftar say 7-17-2009.
Here is the link for the webshot pics. http://rides.webshots.com/album/573406717BReylJ
Thanks, Roy

[Miami Mike]

Welcome to RCGroups!

I understand that you're new here, but I'm curious about how you managed to dig up and resurrect a thread that died over 5-1/2 years ago about a problem with defective wing construction in Bird of Time gliders. How did you find this thread? Why didn't you just start a new thread?